1. Field of the Invention
This invention relates generally to fire hydrants, and more particularly to improvements in fire hydrants of the frostproof type.
2. Statement of the Prior Art
Fire hydrants of the type including a valve stem and a connected valve supported for reciprocating movement in a vertical barrel are, of course, well known. Typically, such hydrants include a bonnet secured to the barrel, the bonnet having an internally threaded aperture which receives the externally threaded upper end of the valve stem. In such hydrants, the valve stem is reciprocated by rotating the valve stem relative to the bonnet. Generally, the valve stem is rotated by a wrench or the like which fits about a suitably shaped projection at the top of the valve stem which protrudes through the bonnet. Fire hydrants fitting this general description may be found in sales brochures distributed by Waterous, South St. Paul, Minnesota; Kennedy Valve Manufacturing Co., Inc., Elmira, New York; United States Pipe and Foundry Company, Smith Valve and Hydrant Division, East Orange, New Jersey; and Clow Corporation, Eddy-Iowa Division, Oskaloosa, Iowa.
The desirability of relying on the water pressure in the shoe connecting the barrel to the water supply line to bias the valve to the closed position to prevent flooding in the event of traffic damage has also been recognized. Hydrants operating according to this principle are also disclosed in the above-mentioned literature.
Still others have recognized that the accumulation of water and subsequent freezing thereof between the mating threads of the bonnet and the valve stem can block reciprocating movement of the stem to open the valve. Based on this, fire hydrants using means other than mating threaded members to accomplish reciprocating movement of the valve stem and connected valve have been suggested. See, for example, U.S. Pat. Nos. 3,532,108 and 3,532,109, wherein the valve stem is reciprocated by a detachable mechanism securable to the bonnet for engagement with the top of the valve stem protruding therethrough. In both patents, the hydrant disclosed is of the type wherein the valve is biased to the closed position by the water pressure in the shoe.
Because of the absence of a threaded connection between the valve stem and the bonnet, the hydrants disclosed in these patents include coil springs for holding the valve stem in the closed position in the event of reduced water pressure or vacuum in the shoe. In U.S. Pat. No. 3,532,108, one end of the coil spring is seated on the bottom of the shoe and the other end is secured about a projection on the bottom of the valve. In U.S. Pat. No. 3,532,109 the coil spring is disposed about the valve stem and has one end seated on a shoulder in the bonnet and the other end seated on a flange on the stem. In arrangements of this type, it is apparent that the coil spring is compressed each time the hydrant is operated to reciprocate the valve stem. Thus, after a period of time, these springs lose their elasticity and may even break. Moreover, the spring may be difficult to replace when it is located in the valve shoe as disclosed in U.S. Pat. No. 3,532,108.